1. Field of the Invention
The present invention relates to a high-frequency circuit apparatus having a printed circuit board provided with high-frequency circuits mounted thereon.
In a multiplex radio communication system, transmitter and receiver portions, such as mobile base station devices, are mounted on a single printed circuit board for the purpose of miniaturization and economy. The receiver and the transmitter mounted on the printed circuit board are isolated by a metal casing or the like. The isolation means can prevent electromagnetic coupling between the transmitter and the receiver through a space on the printed circuit board, but no electromagnetic coupling through the inside of the printed circuit board can be prevented. In particular, if the receiver is of high sensitivity, it is necessary to prevent electromagnetic coupling through the printed circuit board.
2. Description of the Related Art
In a known high-frequency circuit apparatus, an array of plated through holes is provided between the high-frequency circuits to prevent electromagnetic coupling between the high-frequency circuits.
However, only one array of the plated through hole is not enough to sufficiently reduce leakage power. To sufficiently reduce the leakage power, in the conventional high-frequency circuit apparatus, the high-frequency circuits are each covered by a metal casing to isolate them from one another. However, the isolation means such as the metal casing cannot prevent electromagnetic coupling of the circuits through the printed circuit board, as mentioned above, and the high-frequency circuit apparatus becomes large as a whole.